The purpose of this research is to develop indices of vulnerability for schizophrenia in adults in order to make possible the identification of individuals with a high risk for developing this disorder. Psychological, psychophysical and psychophysiological measures which have been demonstrated to differentiate between schizophrenics, patients with affective disorders, and normal controls will be applied to newly admitted schizophrenic patients, their siblings and their discordant monozygotic co-twins. Initial and follow-up testing will be done to determine whether the measures in question are state or trait-related, and whether they are markers of genetic or extragenetic (acquired) vulnerability to schizophrenia. Subjects will be assigned to diagnostic groups according to the GMS diagnostic interview used in the US-UK study of the diagnosis of mental disorders. The psychophysiological measures to be used are pupillography, evoked potential, visual temporal integration, auditory threshold, auditory facilitation, cross-modal reaction time, and smooth pursuit eye movements. Additional measures of vulnerability include speech comprehensibility and Antonovsky's coping resourses for the life event scale. The impact of Life Events will be assessed by the Holmes-Rahe procedure, and competence in every day life will be measured by the SSIAM and Zigler-Phillips Scale.